fix: Only check for discriminator conflicts on STI entities (#2985)

If an entity has the same discriminator value as one using `TableInheritance` this should be allowed as 
there is no way for them to conflict.

This commit also fixes the discriminatorColumn 
check to check all the entities it should be
checking. Only the parent in an STI setup has the
"STI" inheritancePattern, the children just have the 
"entity-child" tableType. Before two children with 
the same discriminatorValue would be
(incorrectly) allowed as they'd never even get 
checked.

Fixes #2984

src/metadata-builder/EntityMetadataValidator.ts

@@ -58,15 +58,18 @@ export class EntityMetadataValidator {
 
         // validate if table is using inheritance it has a discriminator
         // also validate if discriminator values are not empty and not repeated
-        if (entityMetadata.inheritancePattern === "STI") {
+        if (entityMetadata.inheritancePattern === "STI" || entityMetadata.tableType === "entity-child") {
             if (!entityMetadata.discriminatorColumn)
                 throw new Error(`Entity ${entityMetadata.name} using single-table inheritance, it should also have a discriminator column. Did you forget to put discriminator column options?`);
 
             if (["", undefined, null].indexOf(entityMetadata.discriminatorValue) !== -1)
                 throw new Error(`Entity ${entityMetadata.name} has empty discriminator value. Discriminator value should not be empty.`);
 
             const sameDiscriminatorValueEntityMetadata = allEntityMetadatas.find(metadata => {
-                return metadata !== entityMetadata && metadata.discriminatorValue === entityMetadata.discriminatorValue;
+                return metadata !== entityMetadata
+                    && (metadata.inheritancePattern === "STI" || metadata.tableType === "entity-child")
+                    && metadata.discriminatorValue === entityMetadata.discriminatorValue
+                    && metadata.inheritanceTree.some(parent => entityMetadata.inheritanceTree.indexOf(parent) !== -1);
             });
             if (sameDiscriminatorValueEntityMetadata)
                 throw new Error(`Entities ${entityMetadata.name} and ${sameDiscriminatorValueEntityMetadata.name} have the same discriminator values. Make sure they are different while using the @ChildEntity decorator.`);

test/github-issues/2984/entity/commit/note.ts

@@ -0,0 +1,9 @@
+import {Entity, PrimaryGeneratedColumn} from "../../../../../src";
+
+@Entity({name: "commitNote"})
+export class Note {
+
+    @PrimaryGeneratedColumn()
+    public id: number;
+
+}

test/github-issues/2984/entity/issue/note.ts

@@ -0,0 +1,10 @@
+import {Entity, PrimaryGeneratedColumn, TableInheritance} from "../../../../../src";
+
+@Entity({name: "issueNote"})
+@TableInheritance({column: {type: "varchar", name: "type"}})
+export class Note {
+
+    @PrimaryGeneratedColumn()
+    public id: number;
+
+}

test/github-issues/2984/entity/issue/ownernote.ts

@@ -0,0 +1,10 @@
+import {ChildEntity, Column} from "../../../../../src";
+import {Note} from "./note";
+
+@ChildEntity()
+export class OwnerNote extends Note {
+
+    @Column()
+    public owner: string;
+
+}

test/github-issues/2984/entity/wiki/note.ts

@@ -0,0 +1,10 @@
+import {Entity, PrimaryGeneratedColumn, TableInheritance} from "../../../../../src";
+
+@Entity({name: "wikiNote"})
+@TableInheritance({column: {type: "varchar", name: "type"}})
+export class Note {
+
+    @PrimaryGeneratedColumn()
+    public id: number;
+
+}

test/github-issues/2984/entity/wiki/ownernote.ts

@@ -0,0 +1,10 @@
+import {ChildEntity, Column} from "../../../../../src";
+import {Note} from "./note";
+
+@ChildEntity()
+export class OwnerNote extends Note {
+
+    @Column()
+    public owner: string;
+
+}

test/github-issues/2984/issue-2984.ts

@@ -0,0 +1,21 @@
+import "reflect-metadata";
+
+import {closeTestingConnections, createTestingConnections, reloadTestingDatabases} from "../../utils/test-utils";
+import {Connection} from "../../../src";
+
+describe("github issues > #2984 Discriminator conflict reported even for non-inherited tables", () => {
+
+    let connections: Connection[];
+    before(async () => connections = await createTestingConnections({
+        entities: [__dirname + "/entity/**/*{.js,.ts}"],
+    }));
+    beforeEach(() => reloadTestingDatabases(connections));
+    after(() => closeTestingConnections(connections));
+
+    it("should load entities even with the same discriminator", () => Promise.all(connections.map(async connection => {
+        connection.entityMetadatas.should.have.length(5);
+        connection.entityMetadatas.forEach(metadata =>
+            metadata.discriminatorValue!.should.be.oneOf(["Note", "OwnerNote"]));
+    })));
+
+});